Snape and DADA

[bamajenny12]

No: HPFGUIDX 111917

Just a question that keeps popping into my head. Does anyone
else ever wonder WHY Snape has never gotten the DADA
position? We read repeatedly that Snape wants the position,
and Dumbledore trusts Snape, so why does Dumbledore not
give Snape the one teaching position that Snape really wants?

Jenny
ps: If this has been answered some where in the books, please
forgive me and tell me where, because for the life of me I don't
remember it.